A known valve mechanism discharges a fluid such as a drain or steam from a valve port. Such a valve mechanism has the problem of clogging of the valve port caused by foreign matter included in the fluid and deposited on the valve port. A technique for solving this problem is disclosed in Japanese Patent Application Publication No. 2001-27391, for example. In the technique disclosed in Japanese Patent Application Publication No. 2001-27391, a foreign matter removing member disposed in the valve port (orifice) is caused to roll by a fluid passing through the valve port to thereby automatically remove foreign matter attached and deposited on the valve port.